You need to get calories from somewhere, should it be from carbohydrate or fat?

Monday, May 30, 2011

Energy expenditure in obese vs slim non dieters

Just before I get back to the prolonged fasting and weight loss post I thought I'd put this picture up.

It's slightly modified for clarity and taken from Fig 1 of this paper.

None of the 10 people in either column are being dieted, the graphs would be different under caloric restriction. I would, all things being equal (ie a linear relationship from thin through obese to a BMI of 50), expect the obese subjects to use/lose more adipose calories per day in proportion to their obesity if you suddenly withdrew all food.

They don't.

There's more on the study here, which has all of Fig 1 and has not been subjected to my activity with a rubber (OK, an eraser if that's less risque).

35 comments:

Nice Peter. One thing to bear in mind is the wild variation in NEAT among individuals, which makes a means comparison a little difficult and yet may explain a lot why some people are better at losing body fat than others:

bit.ly/cL7evu

The TEF part makes me wonder if it leads to some type of inertia. Bodybuilders seem to be very effective at losing body fat by eating many small meals per day, typically low calorie meals.

Not optimal in my mind in terms of overall health, but perhaps an effective short-term strategy for losing body fat.

But there is more that needs to be added to that schematic - amylin is missing and I think something with leptin and interleukins.

(I think we need a schematic for adipose tissue regulation, insulin, leptin - or perhaps the whole thing should be expanded into one large schematic. )

I do know that when I was attempting to lose weight on a low-fat diet I would get cold - even if TSH was normal. Not so on a low carb diet. Why?

And why does a low carb diet reduce appetite when a low fat fails to? It would seem that amylin (a leptin cofactor) is secreted with insulin (in what amounts I don't know - or how regulated?) would tend to have the opposite effect!

First thing I wondered about the chart was why people spent so much energy telling lies. Then I thought it must be an attempt to explain all the assertions about fat people having deficient personalities that affect their results in diet studies.

I just looked (briefly) at the study, and the conclusion is based on some regression of weight gain on insulin sensitivity (among other variables). This is used to conclude causation which is clearly problematic. Why not do the regression the other way with regressing insulin sensitivity on weight gain...

Ellen, it's even weirder because it's "no effect on weight changes," either up or down, that were more prevalent in people with a BMI over 26. Even though up was about half again as likely as down.

But of course it's an observational study, not a controlled trial and it doesn't necessarily account for people's consumption of insulin-releasing materials.

It also suggests a behavioral explanation. Skinnier people will tend not to change the behavior that kept them skinny, but fat people who are getting fatter will either continue the behavior that's making them fatter or change their behavior to one that makes them skinnier.

Physical (muscular) work only accounts for 20% of energy consumption. Heat accounts for the other 80%.

WW2 US Army experiments showed that soldiers used only 1500Cal in the tropics vs 6000Cal in the Arctic for identical workloads. This is equivalent to burning nearly 200kg more fat each year in a cold climate.

Obese people are better insulated and have lower surface/volume ratio.

The real key to weight loss is wearing far less clothing and having much cooler houses and work places (18C rather than 25C) not calorie restriction and more exercise. We should feel cool bordering on cold at all times.

The Ethiopian Highlands where humans evolved are only around 20C during the day and frequently very cold at at night. Yet naked hominids lived there for millions of years.

Good point, blogblog. It makes intuitive sense (and I've been known to sleep without covers for this exact reason), however, I wonder if this theory is like exercise with its compensatory increase in appetite? For example, does daytime BMR compensate for this nighttime increase?

I think unless lowering temperature alters something at the cellular level to correct for the insulin resistance, or whatever is causing the obesity, then you probably just have another factor that has a compensatory mechanism elsewhere to keep the "setpoint" stuck where it was in the first point. Just a thought.

Blogblog, I know you don't care for Doug McGuff, but incidentally he recommends drinking 2 litres of ice cold water a day for fat loss because the body's caloric expense in bringing it up to 37ºC burns something like 200 kcals a day. While according to Taubes, having 5 lbs more muscle only burns 25 extra kcals a day.

Agunther: It's more like at most 74 cal/day. A calorie = amount of energy to raise 1g H2O 1 degree C. Food calories are actually kilocalories. So 2L ice water = 2kg ice water. If the water is brought up to body temp before being excreted that's 2kcal per degree x 37 = 74 kcals.

The cold shower, plunge or doing something to induce shivering is probably a more effective strategy. Your body would need to expend energy to keep a far greater mass at 37 than 2kg.

@karl: Reduction in NEAT is documented with calorie restriction. The greater the restriction, the greater (on average) the reduction in NEAT.

@all: This assumes RMR remains constant. It goes down in response to caloric restriction.

Northern European peasants spent as much as 3-5 months a year resting in bed to save energy. This only ended during the Industrial Revolution when the risk of starvation disappeared.

If you look at global obesity levels vs climate you will see quite a strong correlation (roughly 0.7). Hot humid climates are by far the hardest to lose body heat in.

Living in a hot humid climate drastically reduces appetite (if you don't have air conditioning).

I'm sure the consumption of sugary drinks rather than plain water in hot weather is a major factor in modern obesity. Two litres of Coke is an extra 860 calories.

The lowest obesity levels are in Korea and Japan which have cold climates. The highest obesity levels are in Melanesia and Mexico.

The highest obesity levels in the US are in the Deeps South. The lowest levels are in the Northeast

In Europe obesity is highest in the Mediterranean and lowest in Finland.

Unfortunately people tend to wear more clothing in air-conditioned buildings which negates the cooling effect. It also overcomes the loss of appetite caused by high body temperature.

I'm always amazed how people try to sleep in hot rooms covered with quilts. We need to be really cool (but not cold) to sleep properly.

As well as accepting a bit of cold we should also learn to cope with moderate hunger. Both do us a lot of good.

Chewing or sucking ice is an exceptionally effective way to cool the body. Eating frozen snow to rehydrate can cause fatal hypothermia. Polar explorers always ate their food and drinks as hot as possible to maximise energy intake.

Hey, Carbsane, that 74 kcal is likely pretty reproducible in a bomb calorimeter, but humans are not bomb calorimeters. We do not process energy in the same way. Heat/cold is not conducted across membranes with the same conductance as it is across metal surfaces. Enzyme efficiency might also be affected by a change in temperature, etc. I don't know if the 200 kcal estimate is accurate, but given that we aren't bomb calorimeters, it's reasonable to assume it might be plausible. I'd think.

It's more like at most 74 cal/day. A calorie = amount of energy to raise 1g H2O 1 degree C. Food calories are actually kilocalories. So 2L ice water = 2kg ice water. If the water is brought up to body temp before being excreted that's 2kcal per degree x 37 = 74 kcals.

That isn't correct. There are two separate processes - melting the ice and heating the water.

He is not correct. The process in question is drinking 2l of ice water, not eating 2kg of ice chips. The vast majority of the ice will melt in the glass--i.e. outside the body--to keep the water cool. You might net another 2 or 3 kcals melting microscopic ice crystals and the occasional swallowed chunk of ice.

Also, if you're eating straight ice, it's rather rare in practice to find ice as a stable solid at precisely the transition temperature. So you would need to bring the ice up to temp from, say, -13C (my freezer temp) as well as melt it and heat the water, which nets another 55 kJ or 13 kcal since the specific heat of ice is 2.108 kJ/kg*K.

This is interesting. I wonder how many cold drinks Peter is necking during the day to burn through 3000 kcals?

To add more gasoline to this fire, McGuff also says that staying hydrated has an overall net fat-loss effect because it signals that the environment is abundant with food. In his reasoning, dehydration is perceived by the body as drought, which is usually followed by famine. This tells the body to store fat (whether through higher insulin, higher appetite, or some other factor I don't know of) because game/vegetation will soon be scarce.

The body's perception of the abundance/scarcity in its surroundings is a field we haven't discussed much of yet here. Sounds like Stephan's territory.

@blogblog: iceWATER is liquid. Now if someone is chewing and swallowing 2 liters worth of ice*, then your calculation would be correct. Good luck with that one. A dentist friend of mine really frowns on chomping ice cubes.

*and that would have to be more volume of ice since ice is less dense than water to be equivalent to 2kg H2O

@Poisonguy: C'mon man. Are you suggesting that it takes a different amount of energy to heat 2kg of water up 37 degrees in a human body than, say, for the sun to heat it in a bucket? We do not "metabolize" water to warm it up!

I take BCAAs after weight training. The nicest way to take them is to dump them into a Vitamix blender and whip them together with ice cubes.

The net effect is something like a frozen Daquiri, and it is VERY cold (enough for a classic ice-cream headache if you drink too fast).

Drinking large volumes of ice water has a number of other effects apart from requiring the warming of the fluid to body temperature. It also stops the digestive system in its tracks, slows the rate of absorption of the water through the intestines, and probably has many other effects of which we are unaware.

Speaking as someone whose academic background is in thermodynamics, I don't feel that any of the heat capacity calculations here are all that relevant. Be it ice or be it cold water, we don't accomplish heat transfer with percect reversibility nor do we generate heat with perfect efficiency--and changing local body temperature also alters enzyme activity (and probably does a thousand other things as well).

That said, I have to agree with CarbSane that you probably get a stronger effect on calorie burn through cold-water immersion than by drinking it.

Many ears ago I was at a very hot nightclub. I started drinking ice water (mostly ice). After about 6-8 glasses I began shivering. It was a really bizarre experience to be shivering in a hot place.

In practice ice standing in a glass is always at OC. As soon as it is taken out of the freezer some of it melts and forms a eutectic mixture. The temperature of the ice/water mix remains constantly at 0C until the ice has completely melted. Ice water baths are often used in laboratories as a simple way to maintain a constant temperature of exactly 0C.

Blogblog at 12:44PM:It is indeed highly relevant what happens at the cellular level. Search mitochondrial respiration and uncoupling as the source of thermogenesis or proton leak across the mitochondrial membrane. From there it's a short jump to ROS management and health. Hints: expression of uncoupling protein does not come from carb consumption and ability to rapidly switch from heat generation to ATP production is a feature of health. Nick Lane's Sex, Power and Suicide is a good source.

I will repeat myself. Knowing the underlying cellular mechanisms is absolutely irrelevant to human health.

Humans were far healthier (except for trauma and infections) before they had any formal understanding whatsoever of medicine or physiology.

The increase in longevity in the past 100 years is almost entirely due to increased hygiene (clean drinking water, sewerage and refigeration) not medicine.

The wild birds in my backyard "know" far more about nutrition and a healthy lifestyle than any human experts. It was demonstrated as early as the 1920s that chickens given a choice of natural foods could easily achieve a far more balanced diet and better weight control than a diet formulated by the leading animal nutrition experts.[Wild chickens eat mostly small invertebrates and leafy greens not seeds].

The very idea that we can fully understand and control cellular processes is a mixture of complete arrogance and utter delusion. It is many orders of magnitude more complex than controlled nuclear fusion. It won't happen in 10 years, 100 years or probably even in 1000 years.

In 2002 Professor Peter Doherty, a Nobel Laureate in immunology, gave a speech on the 50th anniversary of the publication of the structure of DNA. He said that no major medical breakthrough had been achieved via genetics in the previous 50 years. He added that it was quite possible that any major breakthroughs would take another 50 years. The US national Institutes of Health gave a similar bleak opinion of the almost futile 25 year "War on Cancer".

[It should be noted than none of the co-discovers of DNA had any prior training in medicine or genetics (Maurice Wilkins- chemist, James Watson - ornithologist, Francis Crick - physicist].

That paper at http://www.ncbi.nlm.nih.gov/pubmed/21617179 Body Weight, Not Insulin Sensitivity or Secretion, May Predict Spontaneous Weight Changes in Nondiabetic and Prediabetic Subjects: The RISC Study

is troubling - I know that insulin plays a roll - I've seen the fat deposits at injection sites of people taking insulin.

Could be that the role of leptin, lectins, triglyceride induced leptin resistance is dominates? Like to see a controlled study.

Just about everyone who has even been on a diet knows that the heavier you are, the faster you lose, and that the infamous "last 10 lb" are by far the hardest and slowest to go. Seriously, just ask anyone who has been on a diet for more than a few months. Initial water loss or small samples might obscure the difference, but it exists.

About Me

I am Petro Dobromylskyj, always known as Peter. I'm a vet, trained at the RVC, London University. I was fortunate enough to intercalate a BSc degree in physiology in to my veterinary degree. I was even more fortunate to study under Patrick Wall at UCH, who set me on course to become a veterinary anaesthetist, mostly working on acute pain control. That led to the Certificate then Diploma in Veterinary Anaesthesia and enough publications to allow me to enter the European College of Veterinary Anaesthesia and Analgesia as a de facto founding member. Anaesthesia teaches you a lot. Basic science is combined with the occasional need to act rapidly. Wrong decisions can reward you with catastrophe in seconds. Thinking is mandatory.
I stumbled on to nutrition completely by accident. Once you have been taught to think, it's hard to stop. I think about lots of things. These are some of them.

Organisation (or lack of it)!

The "labels" function on this blog has been used to function as an index and I've tended to group similar subjects together by using labels starting with identical text. If they're numbered within a similar label, start with (1). The archive is predominantly to show the posts I've put up in the last month, if people want to keep track of recent goings on. I might change it to the previous week if I ever get to time to put up enough posts in a week to justify it. That seems to be the best I can do within the limits of this blogging software!